The present application relates to the subject matter of five coassigned applications: VERSATILE ANTENNA ARRAY FOR MULTIPLE PENCIL BEAMS AND EFFICIENT BEAM COMBINATION, application Ser. No. 08/808,347; MULTI-CHANNEL MULTI-BEAM ENCODING SYSTEM, filed on May 22, 1997; METHOD AND APPARATUS FOR ADAPTING OMNIDIRECTIONAL SYNCHRONOUS WIRELESS COMMUNICATIONS PROTOCOL TO SECTORIAL ENVIRONMENTS, filed on May 22, 1997; IMPROVED TWO-WAY PAGING UPLINK INFRASTRUCTURE, filed on Aug. 19, 1997; and CONFLICT RESOLUTION IN A MULTI-BEAM MULTI-SITE PAGING SYSTEM, filed on Nov. 17, 1997. The contents of these co-assigned applications are herein incorporated by reference for all purposes.
The present invention relates generally to two-way paging networks and more particularly to subscriber unit transmission power control in two-way paging networks.
Two-way paging systems that allow individual subscriber units (SUs), or pagers, to both receive paging information and transmit responses are becoming more prevalent. An SU may either be mobile, such as with portable pagers, or stationary, such as an SU in a vending machine for status reporting. It will be recognized that the invention has a wide range of applicability; it can also be applied to any type of individual wireless receiver/transmitter used in a two-way pager network. In prior art two-way pager networks, the transmission power used by individual SUs to transmit responses is not controlled. An SU transmits information using a constant power level, regardless of either the physical distance to a base station within the paging network, or the clarity of the inbound signal received at the base station.
Several problems arise in this situation, which can be explained with reference to FIG. 1. FIG. 1 depicts a two-way paging network 100. This network is not represented to be prior art, but relates to paging infrastructure as disclosed in co-assigned applications listed above, which are herein incorporated by reference. Network 100 includes a regional controller 101, a plurality of base stations 105, and a plurality of subscriber units (SUs) 110.
Base station 105 utilizes a multi-beam concept by sending signals to the SUs 110 on outbound beams 115, and receiving signals from SUs 110 on inbound beams 120. Preferably, inbound beams 120 and outbound beams 115 are coincident, but in practice they may be skewed from each other as displayed in FIG. 1. Base station 105 may also utilize an omni-directional antenna, which is also disclosed in the co-assigned applications listed above, and herein incorporated by reference.
On occasion, different SUs will send data at the same frequency at the same time. This gives rise to a possibility that SU transmissions will interfere with one another. Compounding the interference problem is an inability of current two-way pager networks to control or vary the level of SU transmission power.
Other problems arise where SU transmission power levels are uncontrolled. First, when the range, or distance, from the SU to the base station is short, a SU may expend excessive energy in transmitting responses. This negatively effects the efficiency and lifetime of the SU""s power source. Second, an SU that transmits at excessive power levels at any distance from the base station may interfere with the transmission of another SU that transmits on the same frequency at the same time. Because of its distance from the base station or due to other transmission propagation conditions, the transmissions from the other SUs may hardly be received at a base station or possibly cancelled out by an SU transmitting at an excessive power level.
What is needed is a two-way paging system that supports the capability of controlling transmission power level of individual subscriber units.
The present invention provides a method and system for controlling subscriber unit transmission power levels in a two-way paging network. The ability to adjust the power level of individual SUs saves critical power resources yet ensures that the SU""s transmissions are received at a base station in a paging network. Power control in a two-way paging network further lessens the possibility of interference among multiple SUs transmitting at the same time.
In accordance with a first aspect of the present invention, a method is provided for receiving at a subscriber unit a communication containing a power control command. In response to the power control command, the subscriber unit adjusts its transmission power.
In accordance with a second aspect of the present invention, a method is provided for controlling subscriber unit transmission power in subscriber unit-initiated communication sessions using ReFLEX protocol standards developed by Motorola Inc. of Schaumburg, Ill.
In accordance with a third aspect of the present invention, a method is provided for controlling subscriber unit transmission power levels in base station-initiated communication sessions using the ReFLEX protocol standard.
In accordance with a fourth aspect of the present invention, a two-way paging network is provided for allowing a SU""s transmission power to be controlled. The paging network. includes: a plurality of subscriber units having a receiver and a transmitter, a plurality of base stations for sending and receiving data and for sending to selected subscriber units a power control command, and a regional controller for directing communication between individual subscriber units and individual base stations. Further, selected subscriber units include a power control system for controlling transmission power levels of data signals sent to a selected base station.
In accordance with still a fifth aspect of the present invention, a subscriber units apparatus for use in a two-way paging network includes: a receiver, a transmitter, and a power level controller. The power level controller responds to a power control command received from a paging network to adjust the power level of the transmitter for subsequent transmissions. The power control command sets a power level of a subscriber units""s transmissions to ensure that a subscriber units apparatus""s successful transmission to a base station, while decreasing the such transmission""s interference with other subscriber units"" transmissions.
The above discussion has been in terms of pager systems, but the invention applies the same principle to cellular communications in general. For example, the present invention could be adapted for use with multiple stationary subscriber units that transmit large amounts of data on a reverse channel to paging network. A further understanding of the nature and advantages of the invention herein may be realized by reference to the remaining portions of the specification and the attached drawings.